The present invention relates to a system for controlling the opening of a throttle valve of a vehicle.
In general, when a vehicle incorporating a gasoline engine is decelerated, the vacuum in the intake manifold to the engine is increased, making the intake efficiency of the engine lower with the result that misfire is likely to take place. As a result, a considerable concentration of unburned hydrocarbons is discharged. In order to meet recent regulations to control environmental pollution, it has been proposed that the throttle valve should be controlled so as to improve the burning efficiency. A throttle positioner, for example, electrically senses vehicle speed, thereby producing an electrical signal which actuates a solenoid valve, intermittently transmitting the vacuum in the intake manifold to the diaphragm, thus opening the throttle valve by a predetermined level. The throttle positioner, however, becomes complicated and expensive due to the employment of expensive devices including a vehicle speed senser, a computer and a vacuum switching solenoid so as to electrically sense and control vehicle speed.